12C docs still state: Oracle performs a correlated subquery when a nested subquery references a column from a table referred to a parent statement one level above the subquery. (Using Subqueries). However it allows referencing parent on any level:

I've seen this behavior in one of early 10G releases which then was "fixed" (I'd rather prefer Oracle to leave it and "fix" documentation) in later releases. So I assume same story is going on with 12C. I assume if 12C would allow correlation on any level Oraclewould mention it in New Features, but deep inside I am hoping correlation on any level will stay. Does anyone have any insight? And why am I hoping? New 12C procedure expand_sql_text in dbms_utility package shows how correlation is resolved: